@DNSB - I'm not seeing any failures personally trying the Smarten Punctuation feature this just now, but not surprised there may be edge cases where this happens.
Can you please give this version a whirl - I have completely deferred to a calibre implementation:
https://github.com/kiwidude68/calibr...fy_epub-v1.8.5
If people can let me know this is working ok for them I will make it the main release.